Self-sizing adjustable endotracheal tube

ABSTRACT

There is disclosed an endotracheal tube which has a minimal cross-sectional profile for easy viewing of anatomical features during intubation. After the tube is placed into the trachea, the tube is adapted to increase the diameter. In this manner the tube diameter may be expanded to allow for decreased Work of Breathing (WOB) for patient, while not having so large a diameter as to cause tracheal discomfort.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of patent application Ser. No.11/541,297, entitled “Self-Sizing Adjustable Endotracheal Tube”, filedSep. 29, 2006, which is herein incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to medical devices, and more particularly,to airway devices, such as tracheal tubes.

3. Description of the Related Art

This section is intended to introduce the reader to various aspects ofart that may be related to the present invention which is describedand/or claimed below. This discussion is believed to be helpful inproviding the reader with background information to facilitate a betterunderstanding of the various aspects of the present invention.Accordingly, it should be understood that these statements are to beread in this light, and not as admissions of prior art.

In the course of treating a patient, a tube or other medical device maybe used to control the flow of air, food, fluids, or other substancesinto and/or out of the patient. For example, medical devices, such astracheal tubes, may be used to control the flow of one or moresubstances into or out of a patient. In many instances, it is desirableto provide a seal between the outside of the tube or device and theinterior of the passage in which the tube or device is inserted. In thisway, substances can only flow through the passage via the tube or othermedical device, allowing a medical practitioner to maintain control overthe type and amount of substances flowing into and out of the patient.

Tracheal tubes may be used to control the flow of air or other gasesthrough a patient's trachea. Such tracheal tubes may includeendotracheal tubes and tracheostomy tubes. To seal these types oftracheal tubes, inflatable cuffs are sometimes associated with thesetubes. When inflated, these cuffs generally expand into the surroundingtrachea to seal the tracheal passage around the circumference of thetube. A high-quality seal against the tracheal passageway allows aventilator to perform efficiently.

Generally, endotracheal tubes are available in a subset of sizes fromwhich doctors may select the closest approximate size for a particularpatient. The difference in tube sizes may generally reflect bothdifferences in the length of the tube as well as different tubediameters. In particular, doctors may wish to select an endotrachealtube with an appropriate diameter in order to allow the tube to beeasily inserted into the patient while providing the largest possibleairway path for respiratory gases. For example, an endotracheal tubewith too small a tube diameter may be associated with an increased workof breathing for the patient. Conversely, an endotracheal tube with toolarge a tube diameter presents certain disadvantages. For example, ifthe outer diameter of the endotracheal tube is too large, it can becomedifficult to navigate through the larynx and trachea. Thus, too large anendotracheal tube may increase the time it takes to intubate thepatient. Also, a large endotracheal tube can prove somewhatuncomfortable for the patient. For instance, irritation of the trachealwalls can result from increased contact with the endotracheal tube.

SUMMARY

Certain aspects commensurate in scope with the originally claimedinvention are set forth below. It should be understood that theseaspects are presented merely to provide the reader with a brief summaryof certain forms the invention might take and that these aspects are notintended to limit the scope of the invention. Indeed, the invention mayencompass a variety of aspects that may not be set forth below.

There is provided a tracheal tube that includes a distal end portion; anintermediate portion connected to the distal end portion; and a proximalend portion connected to the intermediate portion, wherein theintermediate portion is adapted to change its diameter.

There is also provided a method for sealing a patient's trachea thatincludes inserting an tracheal tube into a patient's trachea; andexpanding a portion of the tracheal tube to conform to the contours ofthe tracheal walls.

There is also provided a method of manufacturing a tracheal tube thatincludes providing a distal end portion; providing an intermediateportion connected to the distal end portion; and providing a proximalend portion connected to the intermediate portion; wherein theintermediate portion is adapted to change its diameter.

There is also provided a tracheal tube that includes: a distal endportion; an intermediate portion comprising an inner layer and an outerlayer connected to the distal end portion; and a proximal end portionconnected to the intermediate portion, wherein the intermediate portionadapted to change its diameter by expanding a gap between the innerlayer and the outer layer.

There is also provided a method for sealing a patient's trachea thatincludes: inserting a tracheal tube into a patient's trachea, whereinthe tracheal tube comprises an inner layer and an outer layer along atleast a portion of the tube; and expanding a gap between the inner layerand the outer layer of the tracheal tube so that the outer layer of thetube substantially conforms to the tracheal walls.

There is also provided a method of manufacturing a tracheal tube thatincludes: providing a distal end portion of a tube; providing anintermediate portion comprising an inner layer and an outer layerconnected to the distal end portion; and providing a proximal endportion connected to the intermediate portion, wherein the intermediateportion adapted to change its diameter by expanding a gap between theinner layer and the outer layer.

There is also provided a method for sealing a patient's trachea thatincludes: inserting a tracheal tube into a patient's trachea; expandinga portion of the tracheal tube to substantially conform to the contoursof the tracheal walls during a period of patient expiration; andcontracting a portion of the tracheal tube so that the tracheal tube hasan outer diameter that is less than the diameter of the tracheal wallsduring a period of patient inspiration.

There is also provided a system that includes: a tracheal tubecomprising a lumen adapted to pneumatically expand or contract adiameter of at least a portion of the tracheal tube; and a medicalmonitor adapted to be operatively coupled to a tracheal tube, themedical monitor comprising instructions for: increasing pressure to thelumen to expand a portion of the tracheal tube to substantially conformto the contours of the tracheal walls during a period of patientexpiration; and decreasing pressure to the lumen to contract a portionof the tracheal tube so that at least a portion of the tracheal tube hasan outer diameter that is less than the diameter of the tracheal wallsduring a period of patient inspiration.

There is also provided a computer readable medium that includes: codefor increasing pressure to the lumen of an expandable-diameter trachealtube to expand a portion of a tracheal tube to substantially conform tothe contours of the tracheal walls during a period of patientexpiration; and code for decreasing pressure to the lumen of anexpandable-diameter tracheal tube to contract a portion of the trachealtube so that at least a portion of the tracheal tube has an outerdiameter that is less than the diameter of the tracheal walls during aperiod of patient inspiration.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the invention may become apparent upon reading thefollowing detailed description and upon reference to the drawings inwhich:

FIG. 1 illustrates an endotracheal tube with an expandable intermediateportion in accordance with aspects of the present invention;

FIG. 2 illustrates an endotracheal tube with an expandable intermediateportion inserted into a patient's trachea;

FIG. 3 illustrates an endotracheal tube with a ribbed expandableintermediate portion in accordance with aspects of the present invention

FIG. 4 illustrates a tracheal tube with an expandable backbone in itsnon-expanded state;

FIG. 5 illustrates the tracheal tube with an expandable backbone of FIG.4 in its expanded state;

FIG. 6 illustrates an endotracheal tube with an expandable intermediateportion as well as an inflatable balloon cuff;

FIG. 7 illustrates an endotracheal tube with a concentric expandableintermediate portion in accordance with aspects of the presentinvention;

FIG. 8 illustrates an endotracheal tube with an alternative embodimentof a concentric expandable intermediate portion in accordance withaspects of the present invention;

FIG. 9 illustrates a contracted tracheal tube with a concentricexpandable intermediate portion that is contracted around a stylet inaccordance with aspects of the present invention; and

FIG. 10 illustrates an expanded tracheal tube with a concentricexpandable intermediate portion and the sylet in accordance with aspectsof the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments of the present invention will bedescribed below. In an effort to provide a concise description of theseembodiments, not all features of an actual implementation are describedin the specification. It should be appreciated that in the developmentof any such actual implementation, as in any engineering or designproject, numerous implementation-specific decisions must be made toachieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

Provided herein are adjustable-diameter medical devices that may assumea relatively small outer diameter for easy viewing of anatomicalfeatures during insertion, making insertion of these devices easier forthe clinician. Further, such devices may decrease patient discomfortduring insertion as their relatively smaller cross-sectional profiles,as compared to a typical endotracheal tube, may not irritate thepatient's internal passageways. For example, once the endotracheal tubehas been inserted into the trachea, both the inner diameter and theouter diameter of the endotracheal tube may be increased in order toseal the tube against the trachea and to increase the total volume ofair that may pass through the tube. An endotracheal tube having a largeenough inner diameter may allow a patient to expend less energy duringexhalation, as respiratory gases may flow more easily in and out of alarger diameter tube. In certain embodiments, the tube outer diametermay be increased to equal the diameter of the trachea. In such anembodiment, the endotracheal tube may provide an enhanced seal againstthe tracheal walls. As the endotracheal tube outer walls may contact thetrachea over its length, the length of the seal may be increasedrelative to a standard cuffed tube, and a longer seal may be associatedwith improved sealing.

The adjustable-diameter tubes as provided herein may be used inconjunction with any suitable medical device. In certain embodiments,the tubes as provided herein may be used in conjunction with a catheter,a stent, a rib or batten, a feeding tube, an intravenous tube, anendotracheal tube, a tracheostomy tube, a circuit, an airway accessory,a connector, an adapter, a filter, a humidifier, a nebulizer, or aprosthetic, in various embodiments.

An example of such a device is an endotracheal tube 10, as depicted inFIG. 1. The endotracheal tube 10 includes a distal end portion 12 forintubation into a patient, an intermediate portion 14, and a proximalend portion 16 for connection to other medical systems, such as aventilator (not shown). The distal end portion 12 may be shaped andsized as in typical endotracheal tubes. Whereas the intermediate portion14 may be made of a structure capable of expanding, discussed in moredetail below, the distal end portion 12 may be made of any suitablematerial that is suitably rigid. For example, the distal end portion 12may be polyvinyl chloride with a hardness of 84-90 Shore A. The relativerigidity of the distal end portion 12 facilitates guiding theendotracheal tube 10 through the patient's larynx and trachea. As such,the distal end portion 12 may generally be more rigid than theintermediate portion 14 to facilitate guidance through these narrowpassageways. Suitable materials for the distal end portion 12 may alsoinclude silicone, rubber, or polyurethane. Generally, the distal endportion 12 may be attached to the intermediate portion 14 by anysuitable means, such as by adhesives or heat sealing, solvent bonding,RF sealing, ultrasonic welding. Alternatively, the endotracheal tube 10may be extruded as a single tube and the intermediate portion may beblow-molded to have relatively thinner walls than the distal end portion12 or the proximal end portion 16. In a specific embodiment, the outerdiameter of the distal end portion 12 may be approximately 1-14millimeters, which may vary depending on whether the patient is apediatric patient or an adult patient. The distal end portion 12 may beany suitable length. For example, in certain embodiments, the distal endportion 12 may be 10-50 millimeters. In addition, the distal end portion12 of the endotracheal tube 10 may include an opening 17 (see FIG. 2) inthe side wall of the distal end portion 12 near the distal opening 18.This opening 17 is often called a “Murphy eye” and may serve as analternate flow path in the event that the distal opening 18 becomesblocked. Also, the distal opening 18 may be beveled to allow forsmoother insertion through the larynx and trachea.

As with the distal end portion 12, the proximal end portion 16 may beformed from conventional plastics or polymers, including medical gradepolyvinyl chloride. Generally, the proximal end portion 16 may beattached to the intermediate portion 14 by any suitable means, such asby adhesives or heat sealing. The proximal end portion 16 may be capableof being attached and detached from other medical systems, including aventilator. As such, the proximal end portion 16 may terminate with acoupling, such as a quick-disconnect coupling (not shown) or a standard15 mm outer diameter coupling. In a specific embodiment, the outerdiameter of the proximal end portion 16 may be approximately 2-11millimeters, which may vary depending on whether the patient is apediatric patient or an adult patient. The proximal end portion 16 maybe any suitable length. For example, in certain embodiments, theproximal end portion 16 may be 0.1-50 or more centimeters. Further, asthe proximal end may be manipulated by healthcare workers during tubeinsertion and connection, in certain embodiments it may be advantageousfor the proximal end portion 16 to be relatively rigid, with a hardnessin the range of 84-90 Shore A. In a specific embodiment, at least aportion of the outer diameter of the proximal end portion 16 may beabout 15-16 millimeters. Such a diameter may allow direct connection ofthe proximal end portion 16 to the ventilator tubing, which mayeliminate a connection piece, providing cost and convenience advantages.

The endotracheal tube 10 may also include any suitable number of lumens(not shown) that may be appropriately sized and shaped for inflation,deflation, or suction. In one embodiment, a lumen may be operativelyconnected to the intermediate portion 14 to assist inflation ordeflation. In another embodiment, a lumen may be disposed on the tube 10and may terminate in notch or hole in the proximal portion 16 placeddirectly above the shoulder of the intermediate portion 14 that allowssuction of any secretions that may build up on the top shoulder of theintermediate portion.

The intermediate portion 14 of the endotracheal tube 10 includes astructure capable of expanding in diameter. As depicted in FIG. 1, theintermediate portion 14 is in a partially expanded state. Theintermediate portion 14 may contract such that its inner diameter isrelatively smaller than the inner diameter of the proximal end portion16 or the distal end portion 12. It should be understood that innerdiameter of the endotracheal tube 10 may generally be measured frominterior wall to interior wall of the tube, and the outer diameter maybe measured from the exterior wall to exterior wall. Further, a maximumexpandable outer diameter of the intermediate portion may be measuredprior to insertion into a patient, as an intermediate portion 14 mayassume a diameter larger than a tracheal diameter when fully expandedbut not inserted into a patient. After insertion into a patient, themaximum outer diameter of the intermediate portion 14 may generallyconform to the tracheal diameter, because the outer diameter can onlyexpand as much as the trachea will allow. In certain embodiments, theintermediate portion 14 may have a range of maximum possible inner orouter diameters that may range from two times the size of an averagetrachea to half the size of the average trachea or smaller. Further, theportion 14 may taper or vary in diameter along its length. It should beunderstood that an average trachea size may be an adult male or femaleaverage size that is based on height and weight, or a child averagesize. For example, an adult trachea may range in size from 14 mm to 27mm, with the average being around 20 mm. In one embodiment, the maximumexpanded inner diameter of the intermediate portion 14 may be onlyslightly smaller than the outer diameter, and may range from 10 mm toslightly less than 60 mm. However, any suitable inner diameter/outerdiameter combination is contemplated, and may depend on the size of thepatient and the use of the device (e.g. veterinary use).

The intermediate portion 14 may also contract to have minimum inner andouter diameters that are suitably small to allow the intermediateportion 14 to be easily inserted into the trachea. In certainembodiments, the contracted inner or outer diameter may be 1-10 mm.However, any suitable contracted inner diameter/outer diametercombination is contemplated.

The intermediate portion 14 may be formed from materials having suitablemechanical properties (such as puncture resistance, pin hole resistance,tensile strength), chemical properties, and biocompatibility. In oneembodiment, the walls of the intermediate portion 14 are made ofpolyurethane having suitable mechanical and chemical properties. Anexample of a suitable polyurethane is Dow Pellethane® 2363-80A or 80AE.In another embodiment, the walls of the intermediate portion 14 are madeof a suitable PVC. Suitable materials may also include polyethyleneteraphthalate (PET), low-density polyethylene (LDPE), polypropylene,silicone, neoprene, or polyisoprene.

In certain embodiments, the intermediate portion 14 may have relativelythinner tube walls than the proximal end portion 16 and the distal endportion 12. For example, an intermediate portion 14 may have tube wallsthat are sufficiently thin to fold in on themselves in order to conformto a patient tracheal diameter. The intermediate portion 14 tube wallsmay be between 5 microns 10 microns and 3 millimeters in thickness. Incertain embodiments, the intermediate portion 14 walls are between 0.2mils (where mils are thousandths of an inch) and 3 mils. Further, incertain embodiments, the intermediate portion 14 may be such that it mayassume a slightly curved shape when expanded inside the trachea. Aslightly curved design may reduce kinking in the endotracheal tube 10that may result from outside forces acting on the device.

In certain embodiments, the proximal end portion 16, the distal endportion 12, and intermediate portion 14 may be formed from the samematerial in an extrusion manufacturing process. In such an embodiment,in order to obtain the varying wall thicknesses of the differentsections of the endotracheal tube 10, a programmable parasin may be usedto vary the wall thickness along the extruded portion. Further, afterextrusion of a suitable length of tube containing all three portions,the intermediate portion 14 may be subjected to a blow-molding processin order to achieve decreased tube wall thickness and increased tubewall flexibility. For example, the endotracheal tube 10 may also be madeby using preextruded tubing and applying heat and pressure appropriatelywithin a molding cavity to achieve the desired shape (blow molding).

These endotracheal tubes 10 can also be formed by extrusionblow-molding, wherein an extruder fed polymer pellets melts the polymerand feeds the molten polymer through a die to form a tube shape. Thisstill molten polymer is then captured in a mold and air pressure isapplied to expand the tube out to the walls of the mold, thus achievingthe desired shape. In the extrusion blow molding process, a core ormandrel of the extruder has apertures to admit a gas such as pressurizedair or an inert gas like nitrogen, into the medical device. After alength of medical device has been extruded, a mold clamps the medicaldevice around the mandrel. As gas is admitted to the intermediateportion 14 area through the mandrel, the intermediate portion 14 expandsagainst the mold.

In the alternative, the intermediate portion 14 wall may be expanded ina second discrete expansion process following an extrusion or moldingprocess, such as with a shuttle blow molding process. This processresults in the area of the tube with larger diameters having thinnerwalls because the same amount of material is stretched over a largerarea. The variable wall thickness, along the length of the endotrachealtube 10 may also be specified in the blow molding process by using aprogrammable parasin on the extruder. A programmable parasin allows thewall thickness being extruded to be controlled as a function of length.Therefore, the extruded section may have walls of varying thickness.

FIG. 3 depicts a specific embodiment in which the intermediate portion14 of an endotracheal tube 10 may include expandable regions 22separated by ribs 20. The ribs 20 are relatively rigid compared to theexpandable regions 22. As depicted, the intermediate portion is in apartially expanded state. However, when fully collapsed, the ribs 20 maybe touching or almost touching while the expandable regions 22 may foldin on themselves, allowing the intermediate portion 14 to substantiallydecrease its inner and outer diameters. Upon application of an expandingforce or apparatus, such as those described herein, the flexibleexpandable regions 22 may unwrinkle and assume their full size, allowingthe inner diameter of the intermediate portion 14 to increase. Forexample, the intermediate portion 14 may be expanded by positivepressure provided by a downstream medical device, such as a ventilator.In other embodiments, the intermediate portion 14 may be expanded by aremovable stent-like apparatus that may be removed prior to removal ofthe endotracheal tube 10.

The ribs 20 provide the advantage of added stability to the intermediateportion, which may ease insertion of the endotracheal tube 10 into thetrachea. In specific embodiments, it is envisioned that the ribs 20 maybe as hard as the proximal end 16 or distal end 12 (e.g. 84-90 Shore Aor 70 shore A). Further, the ribs 20 may be extruded with the expandableregions 22 as part of a single mold by varying the thickness of the moldto accommodate the ribs 20.

In an alternative embodiment depicted in FIGS. 4 and 5, the intermediateportion 14 may include an expandable backbone 24. The expandablebackbone 24 may be formed from a mesh structure that may be made fromany suitable material such as a metal or a polymer. Such an embodimentmay provide the advantage of increased rigidity to the flexibleintermediate portion 14 during intubation. In addition, the expandablebackbone 24 may help maintain the shape of the intermediate portion 14while the intermediate portion 14 is in its expanded state. In certainembodiments, the expandable backbone 24 may be located on the interiorof the intermediate portion 14, or it may be embedded in theintermediate portion 14. In such an embodiment, the walls of theintermediate portion 14 may be sufficiently elastic to allow theexpandable backbone 24 to expand fully.

An expandable backbone 24 is shown in its non-expanded state in FIG. 4and its expanded state in FIG. 5. The cellular design of the expandablebackbone 24 is meant to be illustrative, and it should be understoodthat other configurations and designs, such as coil, mesh or zigzagdesigns, may be appropriate. Any suitable expandable design may be usedfor the expandable backbone 24 of the present invention. In certainembodiments, the cells may be appropriately shaped as to maintainsufficient contact with the tracheal walls such that a seal may besustained.

As mentioned above, the expandable backbone 24 should generally havesufficient elasticity, flexibility, and rigidity to be navigated throughthe larynx and trachea so that it does not abrade the patient's airway.Further, the expandable backbone 24 may be formed in a slightly curvedconfiguration that may improve insertion into the trachea. Accordingly,stainless steel and other common alloys may be used for the expandablebackbone 24. These materials are useful since their flexibility and highmechanical stability ensure they will be expandable and collapsiblewhile at the same time capable of holding their form while in anexpanded state to form a seal against the trachea. The material fromwhich the expandable backbone 24 is formed may have sufficientflexibility to allow for flexing and movements of the trachea. However,one consideration is that the expandable backbone 24 not be so rigid asto be abrasive or to apply undue pressure against the tracheal walls.Additionally, the expandable backbone 24 may be formed from polymericmaterials such as polyethylene terephthalate (PETP), polyurethane andvarious acrylate compositions.

In certain embodiments, the expandable backbone 24 may be formed from ashape memory material such as nitinol. In such embodiments, theexpandable backbone 24 may be substantially stable in both the expandedconformation and the collapsed conformation. Mechanical force, such asforce applied from an expanding apparatus, may be sufficient to triggerthe change from the collapsed state to the expanded state. The expandedstate may be also collapsed by the application of force along at least aportion of the intermediate portion 14. In other embodiments, theexpandable backbone 24 may be mechanically “locked” into an expandedconformation range by mechanical features in the backbone design. Forexample, a diamond-shaped mesh design may include joints at its pointsthat lock into one more possible expanded diameters.

Regardless of the materials used, the expandable backbone 24 may notonly support the flexible intermediate portion 14 of the endotrachealtube 10 but may also be physically attached to the intermediate portion14 by any suitable method, such as with adhesives, mechanicalconnections, or heat bonding. One advantage of having the expandablebackbone 24 physically attached to the intermediate portion 14 is thatit would prevent the two from axially sliding relative to each other. Inaddition, before extubation, both the expandable backbone 24 and theintermediate portion 14 may be collapsed from their expanded states.Having the two physically attached would assist during the collapsingprocess. However, due to the expandable nature of the intermediateportion 14, it may be useful to restrict physical attachment of theexpandable backbone 24 and intermediate portion 14 to certain strategiclocations, allowing the intermediate portion 14 more freedom of motionduring expansion and collapse. As mentioned above, an importantconsideration is that the expandable backbone 24 and intermediateportion 14 may move in unison during the collapsing process prior toextubation.

In certain embodiments, an inflatable balloon cuff 30 as depicted inFIG. 6 may be used in conjunction with the endotracheal tube 10. In thisembodiment, the inflatable balloon cuff 30, instead of the intermediateportion 14, forms the seal against the trachea walls. Typically, theinflatable balloon cuff 30 is disposed, adhesively or otherwise, towardsthe distal end of the endotracheal tube 10 below the vocal cords. Theinflatable balloon cuff 30 may be inflated and deflated via a lumen 32in communication with the inflatable balloon cuff 30, typically througha hole or a notch in the endotracheal tube 10. Further, a lumen (notshown) may be disposed on the tube in order to suction off anysecretions that may build up on the cuff 30.

The inflatable balloon cuff 30 may be formed from materials havingsuitable mechanical properties (such as puncture resistance, pin holeresistance, tensile strength), chemical properties (such as forming asuitable bond to the endotracheal tube 10), and biocompatibility. In oneembodiment, the walls of the inflatable balloon cuff 30 are made ofpolyurethane having suitable mechanical and chemical properties. Anexample of a suitable polyurethane is Dow Pellethane® 2363-90A or 90AE.In another embodiment, the walls of the inflatable balloon cuff 30 aremade of a suitable polyvinyl chloride (PVC). Suitable materials may alsoinclude polyethylene teraphthalate (PET), polyethylene (PE),polypropylene, silicone, neoprene, or polyisoprene.

The intermediate portion 14 may also include a double-layered structurein order to facilitate expansion and collapse. As shown in FIGS. 7 and8, such a double-layered structure may include an inflatable gap betweenthe two layers that may allow the outer diameter of the intermediateportion 14 to expand towards the tracheal walls while simultaneouslyincreasing its inner diameter. FIG. 7 shows an exemplary intermediateportion 14 that includes a concentric outer layer 31 and inner layer 36that are attached to one another by connecting members 38. It isenvisioned that the gap between the inner layer 36 and the outer layer31 may be filled with air or any suitable fluid via a lumen or otherinflation device (not shown) in order to expand the inner diameter ofthe intermediate portion. The connecting members 38 may include holes toallow a single lumen to inflate the gap between the inner layer 36 andthe outer layer 31. Alternatively, several lumens may be used such thateach isolated gap may be filled with air. As the outer layer 31 expandstowards the tracheal walls, inner layer 36 may be pulled along with itby the connecting members 38 in order to increase the inner diameter ofthe intermediate portion 14. The connecting members 38 may be polymeric,and they may be flexible or rigid. In an alternative embodiment, anexemplary double-layered intermediate portion is depicted in FIG. 8which an inner layer 40 is attached to an outer layer 44 at severalattachment points 42 along the intermediate portion. As the inner layer40 is coupled to the outer layer 44, when the outer layer 44 expandstowards the tracheal walls, the inner layer is pulled along, expandingthe inner and outer diameters of the intermediate portion 14. The innerlayer 40 and the outer layer 44 may be spot welded together at only afew attachment points 42 to leave a generally open space between them,such that the space between them may be inflated by a single inflationlumen.

The tracheal tube may also be inserted into the trachea with the aid ofa stylet, in order to facilitate insertion, as well as expansion andcollapse. As shown in FIGS. 9 and 10, a double-layered structure may beinserted in the collapsed state, depicted in FIG. 9, where theintermediate portion 14 is collapsed to closely conform to the diameterof a stylet 46. Both the inner layer 40 and the outer layer 38 may begenerally draped, or furled, around the stylet 46. After insertion, theinner 40 and outer layer 44 may expand towards the tracheal walls, asshown in FIG. 10, and the inner layer 40 may pulled along with the outerlayer 44, expanding the inner and outer diameters of the intermediateportion 14. After successful insertion and inflation, the stylet 46 maybe removed, or, in an alternate embodiment, may remain substantiallyattached to the intermediate portion 14.

Generally, after the endotracheal tube 10 is inserted into a patient'strachea, the diameter of the intermediate portion 14 may be expanded toconform to the tracheal walls, as depicted in FIG. 2. The intermediateportion 14 may inflated to form a seal against the tracheal walls andmay prevent secretions or other detritus from passing through thetrachea into the lungs. The intermediate portion may be inflated insidethe patient's trachea such that its pressure against the tracheal wallsis approximately 20-30 cm H₂O. The intermediate portion 14 may alsoinclude a safety mechanism or other feature designed to prevent thepressure from exceeding a predetermined pressure, such as 50 cm H₂O. Forexample, the intermediate portion 14 may include a pressure valve toallow rapid deflation of the intermediate portion 14. Alternatively, theintermediate portion 14 may include a pop-off section, which is designedto rip or tear at excessive pressures. Such a portion may be made fromgenerally more fragile or thinner material than the rest of theintermediate portion 14.

Possible methods of expansion include mechanical, pneumatic, and/orthermal methods. In one embodiment, radial expansion of the intermediateportion 14 may be accomplished by a mechanical method. Under thismethod, a mechanical expanding apparatus may be inserted within theinterior of the intermediate portion 14 before intubation. Afterintubation, this mechanical expanding apparatus may be used to radiallyexpand the intermediate portion 14 until the intermediate portion 14contacts the tracheal walls. After radial expansion of the intermediateportion 14, the mechanical expanding apparatus may be collapsed to itsoriginal configuration and removed from within the endotracheal tube 10.In certain embodiments, the intermediate portion 14 may be constructedfrom materials with shape memory, such as Nitinol, having a bi-stableconfiguration. In such embodiments, the expanded state of theintermediate portion 14 may have sufficient rigidity to maintain itsgeneral shape after the expanding apparatus has been removed. Themechanical expanding apparatus may also serve the secondary function ofa stylet, which is typically used to guide an endotracheal tube intoplace within the trachea. Use of a stylet may also be advantageous inembodiments in which the intermediate portion 14 walls are soft andthin, as the stylet may provide additional rigidity or column strengthto allow easier insertion of the endotracheal tube 10.

In another embodiment, radial expansion of the intermediate portion 14may be accomplished by a pneumatic method. In this embodiment, aninflatable balloon may be inserted within the interior of theintermediate portion 14 before intubation. After intubation, theinflatable balloon may be inflated, radially expanding the intermediateportion 14 until it contacts the tracheal walls. After radial expansionof the intermediate portion 14, the inflatable balloon may be deflatedand removed from within the endotracheal tube 10.

In an alternative pneumatic expansion, the distal end of theintermediate portion 14 may terminate with a pneumatic cap which isdesigned to yield at a certain pressure range. After intubation, radialexpansion of the intermediate portion 14 may be accomplished by applyingpositive pressure within the endotracheal tube 10 from the proximal endof the endotracheal tube 10. The entire endotracheal tube 10 device maybe designed such that the positive pressure would radially expand theintermediate portion 14 before the pneumatic cap yields to the pressure,at which point the airway of the endotracheal tube 10 may become opened.In another embodiment, the intermediate portion 14 may be inflated anddeflated via a lumen in communication with the intermediate portion 14,typically through a hole or a notch in the endotracheal tube 10. Incertain embodiments, the intermediate portion 14 may be operativelyconnected to a ventilator via the lumen to maintain a substantiallyconstant pressure within the intermediate portion 14.

In yet another embodiment, radial expansion of the intermediate portion14 may be accomplished by a thermal method. Under this method, theinherent physical properties of the material used for the intermediateportion 14 would allow the intermediate portion 14 to radially expandbased merely on temperature differences. For instance, the material forthe intermediate portion 14 may be selected such that its glasstransition temperature would allow a collapsed state at room temperatureand an expanded state at body temperature. In one embodiment, theintermediate portion 14 may include a shape-memory Nitinol, with a shapetransition temperature close to body temperature. In such an embodiment,the shape-memory Nitinol expands when inserted into the body. Retractionmay be accomplished by transferring cooled air through the intermediateportion 14.

Regardless of the method used to radially expand the intermediateportion 14, another method may be required to radially collapse theintermediate portion 14 before extubation. In one embodiment, radialcollapsing of the intermediate portion 14 may be accomplished by amechanical collapsing apparatus, converse to the mechanical expandingapparatus mentioned above. Before extubation, the mechanical collapsingapparatus may be inserted within the endotracheal tube 10 and physicallyattached to the intermediate portion 14. Any number of methods forphysically attaching the mechanical collapsing apparatus may be used.However, one illustrative method is the use of a magnetized mechanicalcollapsing apparatus such that the expandable backbone 24, discussedbelow, is magnetically attracted to it. This method may be useful inembodiments in which stainless steel or other common alloy is used asthe material for the expandable backbone 24. In another embodiment,radial collapsing of the intermediate portion 14 may be accomplishedthrough suction.

Because the intermediate portion 14 may contact the tracheal wallsduring patient intubation, it is also envisioned that it may beadvantageous for the intermediate portion 14 to have a gel coating onits outer diameter in order to place a soft, water-containing layeragainst the tracheal mucosa, instead of a harder plastic material. Thisgel coating may include biologically active agents, for example agentsadapted to promote cell growth or cilia growth. In such an embodiment,therapeutic agents, such as growth factors, may be included on thetissue-contacting surface of the intermediate portion 14 as providedherein. Such agents may include therapeutically beneficial amounts ofbiologically active substances such as FGF (fibroblast growth factor),EGF (epidermal growth factor), PDGF (platelet-derived growth factor),IGF (insulin-like growth factor), TGF-β 1 through 3, cytokines,interferons, interleukins; hormones, insulin, growth hormone-releasingfactor, calcitonin, and/or vitamins such as vitamin C, vitamin E,vitamin A or retinoic acid (e.g. trans-retinoic acid, 13-cis-retinoicacid, 9-cis-retinoic acid, other retinoids and mixtures thereof).

In a specific embodiment, the gel coating as provided herein may includea therapeutic quantity of a retinoic acid in order to promote ciliaregeneration. A therapeutic agent such as a retinoic acid may beincorporated into a mucoadhesive layer disposed on the intermediateportion 14. In certain embodiments, the mucoadhesive layer includes atleast 0.01% retinoic acid. It should be understood that in otherembodiments, the retinoic acid or other therapeutic agent may also beincorporated on the surface of the intermediate portion 14 when amucoadhesive layer is not present.

In other embodiments, it may be advantageous to provide that the gelcoating include a therapeutic agent or a combination of therapeuticagents with a wide variety of biological activities. For example, theagent may include anti-inflammatory, anti-scarification, anticoagulant,antibiotic, antiallergic and antioxidant compounds. Examples of suchanticoagulants include sodium heparin, low molecular weight heparins,heparinoids, hirudin, argatroban, forskolin, vapiprost, prostacyclin andprostacyclin analogues, dextran, D-phe-pro-arg-chloromethylketone(synthetic antithrombin), dipyridamole, glycoprotein IIb/IIa plateletmembrane receptor antagonist antibody, recombinant hirudin, and thrombininhibitors such as Angiomax (Biogen, Inc., of Cambridge, Mass.). Anexample of an antiallergic agent is permirolast potassium. Othertherapeutic substances or agents which may be appropriate includealpha-interferon, genetically engineered epithelial cells, rapamycin,dexamethasone, and functional analogs and structural derivativesthereof. The therapeutic agent may include peptides or proteins (such asenzymes, growth factors, hormones, and antibodies), small moleculecompounds, nucleic acids, lipids, carbohydrates, steroids,glycoproteins, peptidomimetics, and/or oligodynamic metals.

The therapeutic agent may be applied to the surface of the intermediateportion 14 by techniques such as spraying, dipping, covalently bonding,extrusion blow-molding, or cross-linking the agent to the polymericmaterial of the intermediate portion 14. For example, the intermediateportion 14 may be dip-coated by dipping the intermediate portion 14 in asolution containing the compound for a sufficient period of time (suchas, for example, five minutes) and then drying the coated intermediateportion 14, such as by means of air drying for a sufficient period oftime. The agent may be chemically attached to the surface of theintermediate portion 14 through a two-step process surface activationthrough energy activation (e.g. plasma, pulsed plasma, flow dischargereactive chemistry (FDRC), corona discharge) or chemical activation, andsubsequently chemically coupling the agent to the activated surface.Such coupling of the agent to the intermediate portion 14 may beaccomplished through carbodiimide chemistry, reductive amination,malemide-thiol reactions, etc. Further, the therapeutic agent may becompounded with a polymer composition and extruded or molded onto thesurface of the intermediate portion 14 as an outer layer, or it may becompounded into the intermediate portion 14 material itself.

In particular, the nature of the therapeutic agent may dictate itsmethod of attachment to the intermediate portion 14. For example,retinoic acids tend to be relatively hydrophobic, and thus generallyinsoluble in water. In order to incorporate a retinoic acid onto arelatively hydrophilic surface, it may be advantageous to encapsulatethe retinoic acid in amphipathic microspheres that shield thehydrophobicity of the retinoic acid from the hydrophilic polymer on theintermediate portion 14 walls. Such microspheres may enhance delivery ofthe retinoic acid to the mucosa. Proteins such as growth factors mayalso be encapsulated in microspheres to be applied to the surface of theintermediate portion 14. Nanoparticles may also be used to encapsulateor assist in attachment of therapeutic agents to the intermediateportion 14. Fullerenes, micelles or liposheres can all be functionalizedto attach to specific surfaces and provide controlled-release ofhydrophilic or hydrophobic molecules. Alternatively, dendromers can beassembled to contain specific binding sites or adhesion properties andallow for a high concentration of surface groups which may include oneor more therapeutic agents.

The therapeutically beneficial agent may be adapted to be released fromthe intermediate portion 14 over time. For example, the therapeuticagents may be incorporated into a mucoadhesive layer that is adapted todegrade over time, which may allow release of the therapeutic agent. Inother embodiments, a therapeutic agent such as an antimicrobial agentmay be adapted to be released over time via a water-soluble glass. Insuch an embodiment, the intermediate portion 14 may include a metal withantimicrobial properties such as silver in a phosphorus-based glassmaterial that dissolves in water at a rate that may be a function of itsparticular formulation. In one embodiment, a silver calciumphosphorus-based glass may be part of a polymer layer that is made up ofabout 5-10% by weight, e.g. about 7.5% silver calcium phosphorus-basedglass by weight. Such a phosphorus-based glass is available from GiltechLimited, 12 North Harbour Industrial Estate, Ayr, Scotland, GreatBritain KA8 8BN.

The endotracheal tube 10 of the present invention may be incorporatedinto systems that facilitate positive pressure ventilation of a patient,such as a ventilator. These systems may include connective tubing, a gassource, a monitor, and/or a controller. The controller may be a digitalcontroller, a computer, an electromechanical programmable controller, orany other control system. In certain embodiments, the controller mayvary the amount of pressure applied to an intermediate portion 14 inorder to vary the inner diameter of the endotracheal tube 10. Thevariation may occur breath-to-breath in order to move the endotrachealtube 10 away from the patient's tracheal walls and reduce any discomfortassociated with constant pressure of the intermediate portion 14 againstthe tracheal walls. For example, as the work of breathing by the patientis experienced during exhalation, it would be advantageous to have alarger diameter intermediate portion 14 to decrease the work ofexhalation for the patient. However, as inspiration is facilitated bythe pressure of the ventilator, the patient is generally passive duringthis step. Thus, decreasing the diameter of the endotracheal tube 10 maynot substantially affect the patient's work of breathing. Therefore, thecontroller on the ventilator may regularly decrease the pressureassociated with the intermediate portion 14 inflation duringinspiration. For example, if the intermediate portion 14 is designed tocontact the tracheal walls at pressures of 20-30 cm H₂O, a controllermay decrease the intratube pressure to 10-15 cm H₂O. In such anembodiment, it may be advantageous to provide a cuffed endotracheal tube10 in order to maintain positive pressure during such intervals in whichintermediate portion 14 of the endotracheal tube is not sealed againstthe tracheal walls.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

1. A system comprising: a tracheal tube defining a passageway fortransferring gas to a patient's lungs, the tracheal tube comprising: adistal end portion having a distal inner diameter and a distal outerdiameter; an intermediate portion having a double-layered structureconnected to the distal end portion, the intermediate portion having anintermediate inner diameter defined by an inner layer of thedouble-layered structure and an intermediate outer diameter defined byan outer layer of the double-layered structure, the inner layer and theouter layer having a gap therebetween and being coupled to one another;and a proximal end portion connected to the intermediate portion andhaving a proximal inner diameter and a proximal outer diameter, whereinthe distal end portion, the intermediate portion, and the proximal endportion are in fluid communication with one another, and wherein theintermediate portion is adapted to change both the intermediate innerdiameter and the intermediate outer diameter relative to the distalinner diameter and the distal outer diameter and relative to theproximal inner diameter and proximal outer diameter to allow theintermediate outer diameter to contact the patient's tracheal walls; anda medical device adapted to be operatively coupled to the tracheal tubeand being configured to: increase pressure to the gap of theintermediate portion to expand the intermediate inner diameter and theintermediate outer diameter during a period of patient expiration; anddecrease pressure to the gap of the intermediate portion to contract theintermediate inner diameter and the intermediate outer diameter during aperiod of patient inspiration.
 2. The system, as set forth in claim 1,wherein the inner layer and the outer layer are coupled together by aplurality of connecting members.
 3. The system, as set forth in claim 2,wherein the connecting members are perforated to allow gas to flowbetween the outer layer and the inner layer
 4. The system, as set forthin claim 1, wherein inner layer is coupled to the outer layer at aplurality of attachment points.
 5. The system, as set forth in claim 1,wherein the intermediate inner diameter is smaller than the distal innerdiameter and the proximal inner diameter when the intermediate portionis in a relaxed state.
 6. The system, as set forth in claim 1, whereinthe inner layer is pulled along with the outer layer as the outer layerexpands to increase both the intermediate inner diameter and theintermediate outer diameter.
 7. The system, as set forth in claim 1,wherein the medical device comprises a ventilator.
 8. A method forsealing a patient's trachea comprising: inserting a tracheal tube into apatient's trachea, the tracheal tube comprising an intermediate portion,wherein the intermediate portion comprises a double-layered structurehaving an intermediate inner diameter defined by an inner layer of thedouble-layered structure and an intermediate outer diameter defined byan outer layer of the double-layered structure, the inner layer and theouter layer having a gap therebetween and being coupled to one another;and expanding the intermediate portion so that the outer layersubstantially conforms to a tracheal wall during a period of patientexpiration.
 9. The method, as set forth in claim 8, wherein theexpanding the intermediate portion comprises increasing the gap betweenthe inner layer and the outer layer of the double-layered structure. 10.The method, as set forth in claim 8, comprising contracting theintermediate portion so that the intermediate outer diameter is lessthan a diameter of the tracheal wall during a period of patientinspiration.
 11. The method, as set forth in claim 10, wherein thecontracting comprises decreasing pressure through a lumen.
 12. Themethod, as set forth in claim 8, wherein the expanding comprisesapplying pressure through a lumen that terminates in an opening in fluidcommunication with a space between the layers of the double-layeredstructure.
 13. The method, as set forth in claim 8, wherein theexpanding comprises applying pressure through a plurality of lumens thatterminate in a plurality of openings in fluid communication with the gapbetween the inner layer and the outer layer of the double-layeredstructure.
 14. A medical device adapted to be operatively coupled to atracheal tube, the device being configured to: increase pressure to agap between an inner layer and an outer layer of an intermediate portionof a tracheal tube, wherein increasing pressure to the gap expands anintermediate inner diameter defined by the inner layer and anintermediate outer diameter defined by the outer layer, wherein theincrease coincides with a period of patient exhalation; and decreasepressure to the gap of the intermediate portion to contract theintermediate inner diameter and the intermediate outer diameter, whereinthe decrease coincides with a period of patient inspiration.
 15. Thedevice, as set forth in claim 14, wherein the device comprises aventilator.
 16. A tracheal tube defining a passageway for transferringgas to a patient's lungs, the tracheal tube comprising: a distal endportion having a distal inner diameter and a distal outer diameter; anintermediate portion having a double-layered structure connected to thedistal end portion, the intermediate portion having an intermediateinner diameter defined by an inner layer of the double-layered structureand an intermediate outer diameter defined by an outer layer of thedouble-layered structure, the inner layer and the outer layer having agap therebetween and being coupled to one another; and a proximal endportion connected to the intermediate portion and having a proximalinner diameter and a proximal outer diameter, wherein the distal endportion, the intermediate portion, and the proximal end portion are influid communication with one another, and wherein the intermediateportion is adapted to change both the intermediate inner diameter andthe intermediate outer diameter relative to the distal inner diameterand the distal outer diameter and relative to the proximal innerdiameter and proximal outer diameter to allow the intermediate outerdiameter to contact the patient's tracheal walls.
 17. The tracheal tube,as set forth in claim 16, wherein the inner layer and the outer layerare coupled together by a plurality of connecting members.
 18. Thetracheal tube, as set forth in claim 17, wherein the connecting membersare perforated to allow gas to flow between the outer layer and theinner layer
 19. The tracheal tube, as set forth in claim 16, whereininner layer is coupled to the outer layer at a plurality of attachmentpoints.
 20. The tracheal tube, as set forth in claim 16, wherein theinner layer is pulled along with the outer layer as the outer layerexpands to increase both the intermediate inner diameter and theintermediate outer diameter.
 21. A method for sealing a patient'strachea comprising: inserting a tracheal tube into a patient's trachea,wherein the tracheal tube comprises a distal end portion, a proximal endportion, and an intermediate portion co-axially coupled to form aconduit for transfer of gas into the patient's trachea, the intermediateportion comprising an inner layer and an outer layer; and expanding agap between the inner layer and the outer layer of the intermediateportion so that the outer layer substantially conforms to a trachealwall and so that the intermediate portion of the conduit expands ascompared to the proximal portion and distal portion of the conduit,wherein the inner layer of the intermediate portion comes in contactwith the transferred gas.
 22. The method, as set forth in claim 21,wherein the intermediate portion of the tracheal tube is expanded by amechanical method.
 23. The method, as set forth in claim 21, wherein theintermediate portion of the tracheal tube is expanded by a pneumaticmethod.
 24. The method, as set forth in claim 21, wherein the outerlayer and the inner layer are adapted to move together to change anouter diameter and an inner diameter of the intermediate portion. 25.The method, as set forth in claim 21, comprising collapsing theintermediate portion of the tracheal tube.
 26. The method, as set forthin claim 21, wherein the intermediate portion has an inner diameter in arelaxed state that is smaller than a distal inner diameter of the distalportion and a proximal inner diameter of the proximal portion.